chromium/content/browser/renderer_host/commit_deferring_condition_runner.h

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_RENDERER_HOST_COMMIT_DEFERRING_CONDITION_RUNNER_H_
#define CONTENT_BROWSER_RENDERER_HOST_COMMIT_DEFERRING_CONDITION_RUNNER_H_

#include <map>
#include <memory>
#include <vector>

#include "base/memory/ptr_util.h"
#include "base/memory/raw_ref.h"
#include "base/memory/weak_ptr.h"
#include "content/browser/preloading/prerender/prerender_commit_deferring_condition.h"
#include "content/common/content_export.h"

namespace content {

class NavigationRequest;

// Helper class used to defer an otherwise fully-prepared navigation (i.e.
// followed all redirects, passed all NavigationThrottle checks) from
// proceeding until all preconditions are met.
//
// Clients subclass the CommitDeferringCondition class to wait on a commit
// blocking condition to be resolved and invoke the callback when it's ready.
// The client should register their subclass class in
// RegisterDeferringConditions().  Each condition is run in order, waiting on
// that condition to call Resume() before starting the next one. Once the final
// condition is completed, the navigation is resumed to commit.
//
// This mechanism is not applied to about:blank or same-document navigations.
//
// CommitDeferringCondition vs. NavigationThrottle: At first glance this
// mechanism may seem redundant to using a NavigationThrottle (and deferring in
// WillProcessResponse). However, the behavior will differ on pages initially
// loaded into a non-primary FrameTree (e.g. prerendering or BFCached page).
// In these cases NavigationThrottles will run only when the page was loading,
// they will not get a chance to intervene when it is being activated to the
// primary FrameTree (i.e. user navigates to a prerendered page). If the
// navigation needs to be deferred during such activations, a
// CommitDeferringCondition must be used.  It runs both when the navigation is
// loading and when a navigation activates into the primary FrameTree.
class CONTENT_EXPORT CommitDeferringConditionRunner { … };

}  // namespace content

#endif  // CONTENT_BROWSER_RENDERER_HOST_COMMIT_DEFERRING_CONDITION_RUNNER_H_